This invention relates to thermal barriers and, more particularly, to abradable ceramic thermal barrier systems and methods of manufacture.
Components that are exposed to high temperatures, such as gas turbine engine components, typically include a protective coating system having one or more coating layers. For example, turbine blades, turbine vanes, and blade outer air seals typically include the coating system to protect from erosion, oxidation, corrosion or the like and thereby enhance durability or maintain efficient operation of the engine. In particular, conventional outer air seals include an abradable ceramic coating that contacts tips of the turbine blades during engine operation such that the blades abrade the coating upon operation of the engine. The abrasion between the coating and blade tips provides a minimum clearance between these components such that gas flow around the tips of the blades is reduced to thereby maintain engine efficiency.
One drawback of the abradable ceramic coating is its vulnerability to erosion and spalling. For example, spalling may occur as a loss of portions of the coating that detach from the component. Loss of the coating increases clearance between the outer air seal and the blade tips and is detrimental to the turbine engine efficiency. One cause of spalling is the elevated temperature within the turbine section, which causes sintering of the ceramic coating. The sintering causes the coating to shrink, which produces stresses between the coating and the component. If the stresses are great enough, the coating may delaminate and detach from the component.
Accordingly, there is a need for a thermal barrier system having enhanced thermal resistance to resist sintering and shrinkage during engine operation and a method for manufacturing the thermal barrier system. This invention addresses those needs while avoiding the shortcomings and drawbacks of the prior art.